---
title: "About Blue Hour Club | Blue Hour Club"
description: "Blue Hour Club is a small set of free photography calculators, from golden hour times to depth of field, that run entirely in your browser."
url: https://bluehourclub.cyou/about/
---

# About Blue Hour Club

Calculators for the photographer's working day: when the light is good, and how to expose for it.

## What it is

Blue Hour Club has five free tools: a [golden hour and blue hour calculator](https://bluehourclub.cyou/), an [exposure value calculator](https://bluehourclub.cyou/exposure-value-calculator/), a [depth of field calculator](https://bluehourclub.cyou/depth-of-field-calculator/), an [ND filter calculator](https://bluehourclub.cyou/nd-filter-calculator/) with a long-exposure timer and a [print size and DPI calculator](https://bluehourclub.cyou/print-size-calculator/). They are made for planning a shoot and for the arithmetic you would otherwise do on the back of a lens cap.

## How it works

Everything is calculated in your browser. The Sun's position follows Jean Meeus's *Astronomical Algorithms* (2nd edition, 1998) and twilight follows the US Naval Observatory's definitions; we checked sunrise, sunset and twilight against the Naval Observatory's 2026 tables for London, Sydney and Tromsø, and they agree to within about a minute. The photography formulas are the standard ones, and each page shows them with its sources. A built-in list of cities and your browser's own time zone data give local times, so nothing is looked up online.

## What it is not

Light times assume a flat horizon at sea level, and exposure tables describe typical scenes. Your camera's histogram, the weather and the hills on your horizon have the final say.

## Sources

US Naval Observatory, [rise, set and twilight definitions](https://aa.usno.navy.mil/faq/RST_defs). Wikipedia articles on [golden hour](https://en.wikipedia.org/wiki/Golden_hour_(photography)), [blue hour](https://en.wikipedia.org/wiki/Blue_hour), [exposure value](https://en.wikipedia.org/wiki/Exposure_value), [hyperfocal distance](https://en.wikipedia.org/wiki/Hyperfocal_distance) and [neutral-density filters](https://en.wikipedia.org/wiki/Neutral-density_filter). DOFMaster's [depth of field equations](https://www.dofmaster.com/equations.html).